Prototype 73
- The Sega logo has the old "Sega" sound.
- It shatters at the end (like when you get a Game Over) instead of the letters going off the screen thingy.
- Title screen has the E3 demo thingy
- No level select
- No title cards
- A + Start now goes to the Level Complete screen, and then when that is finished it goes to the next act/zone.
- The Level Complete screen:

- All level music is Green Grove Act 1 music.
- All boss music in Final Fight music.
- Knuckles doesn't appear when you shoot out the cannon in Act 1.

- The 2nd zone is Gene Gadget
- Gene Gadget has no boss.

- 3rd zone is Rusty Ruin, and the acts are flipped (Act 2 in the final is Act 1 in this prototype, and Act 1 in the final is Act 2 in this prototype).
- This zone has a boss.

- After beating the Rusty Ruin boss, you go to this screen after the Level Complete screen: